It is well known to provide pressurised fluids such as aerosols, foams etc. in pressurised containers having a valve which is operated, typically depressed in the longitudinal direction of a cylindrical container, by means of an actuator moveably mounted on the container. A typical form of such a container is a cylindrical can with a valve stem extending in the direction of the cylindrical axis. Such a valve is typically reciprocally resiliently operable so that it is depressed by pressure against its resilience to open the valve, and on release of the pressure returns under its resilience to close the valve. One type of such a container is the so called bag-in-can container in which a fluid, typically a viscous gel, is contained within a flexible bag within the container, and a compressed propellant is provided in the space between the container wall and the bag to compress the bag and thereby squeeze the fluid out of the bag, the valve being in communication with the bag. Often such fluids are expandable and include an expansion agent which vapourises when the fluid is exposed to ambient atmospheric pressure after expulsion from the bag to thereby expand the fluid. An example of such a fluid suitable for use in a bag in can container, being a dentifrice, is disclosed in WO-A-01/62212. Typically the expansion agent is isopentane.
A problem with such expandable fluids is that of post-expansion of residual fluid remaining in the outlet conduit of the container immediately upstream of the outlet opening after use. The continued expansion of the fluid can cause the residual fluid to drool out of the outlet opening and cause an unpleasant mess.
A known solution to this problem is the provision of a post-expansion chamber in the actuator upstream of the outlet opening into which residual fluid can expand. It is known to make such post expansion chambers expandable so that residual fluid can be sucked into the post expansion chamber after operation of the actuator. Examples of actuator devices incorporating such a post expansion chamber are for example disclosed in WO-A-2006/013353, U.S. Pat. No. 2,894,660, U.S. Pat. No. 5,732,855 and U.S. Pat. No. 6,264,067. A problem of actuator devices of this state of the art is that residual fluid sucked into the post expansion chamber in this way builds up in volume in the post expansion chamber because it cannot easily evaporate so that the effectiveness of the device gradually declines with time.
It is an objective of the present invention to address this problem and to provide a solution. Other objectives and advantages of the present invention will be apparent from the following description.